PolarStar Fusion Installation Shim Kit

Engine alignment inside the gearbox shell is one of those details that sounds trivial and is not. An engine sitting fractionally out of position will not seal correctly against the hop-up, and the result is inconsistent velocity and poor air efficiency — symptoms people spend a long time blaming on regulators, nozzles and buckings.

Shims set that alignment properly. They are the least expensive component in an HPA installation and among the most likely to determine whether the build shoots the way it should.

Worth keeping on the shelf if you fit engines, or buying alongside one if you are installing yourself. There is nothing more frustrating than a complete build held up by the smallest part in it.

Specifications

Good to know before you buy

A fitting consumable rather than an upgrade. If you are installing a Fusion yourself, order this at the same time — it is the sort of thing you discover you need with the gearbox already open.

Correct shimming is what gives you a proper seal against the hop-up, which is where consistency comes from.

Frequently asked questions

Do I definitely need shims?
It depends on the gearbox and how the engine sits. Many installations need them, and finding out mid-build is inconvenient. It is worth having them to hand.

What happens without correct shimming?
The engine can sit slightly out of alignment, which causes air seal problems, inconsistent velocity and poor efficiency.

Is it Fusion-specific?
This kit is for the Fusion platform. Tell us your engine if you are running something else and we will advise.

Can you fit the engine for me?
Yes, and correct shimming is part of doing it properly.